So-called "compander" systems comprise a compression circuit for volume compression of an information signal before the information signal is transmitted or stored, and further comprise an expansion circuit, for volume expansion, after the transmission or before the reproduction of a previously-stored information signal.
Such systems work, among others, with final control elements to reduce the signal amplitude or to influence the frequency of the signal, where the control signal, required for controlling the primary control element, is derived from the information input signal or the information output signal of the compander circuit.
A known system of this type is disclosed in German Pat. No. 24 06 258. In this known system, an amplifier, constructed as a differential amplifier, is provided in an information signal path for the information signal, and has an inverting input supplied with the information signal and connected, over a feedback path, containing an electronically controllable impedance, with the output of the amplifier. A branch path extends from either the information signal output or the information signal input of the information signal path, and, in this branch path, a control voltage is obtained from the information signal and supplied to the electronically controlled impedance.
Since the circuit components provided for generating the control voltage have, as a rule, unavoidable time constants, with resultant effective delays of the control signal, there is a possibility that, with the rapid rise of the input information signal, the above-mentioned amplifier cannot follow this rise so that a so-called overshoot will appear. Thus, a super-elevated output signal appears briefly at the output of the compander system, on compression. A corresponding likewise undesired effect appears, on expansion, when the amplitude of the input information signal changes very rapidly.